The game of golf includes long stretches of walking and short moments of swinging a golf club to hit a golf ball. Consequently, golf shoes must perform in two different types of movement that have conflicting design requirements. Golf shoes generally include an upper joined to a sole assembly. The sole assembly includes an outsole that contacts the ground. When walking, it is most desirable for the upper and outsole to be soft and flexible so that a golfer's feet are comfortably supported. The upper is more flexible when the laces in the upper are loosely tied. The outsole is soft and flexible by selecting a material with these characteristics and defining flex grooves and notches in the outsole.
When swinging a golf club, great forces are created that may make a golfer's foot move relative to the outsole or make the outsole move relative to the ground. To counteract this tendency, it is desirable for the upper and outsole to be non-deformable and stable. When the laces in the shoe upper are tightly tensioned to tighten the upper, foot movement in the shoe is reduced. The outsole is more stable when made with a rigid material. Thus, the conflict in design requirements is clearly defined.
There have been a number of other proposed solutions to this conundrum. One is for golfers to change shoes between walking and swinging. This solution is undesirable since it would require too much time and effort on the golfer's part. Alternatively, the golfer could adjust their laces between swings, e.g., tightening the laces for swinging and loosening them for walking. This solution is also undesirable because it would also require significant effort from the golfer. Most manufacturers compromise between walking and swinging requirements when making their golf shoes, so that the shoe operates well during both walking and swinging. For example, commonly owned U.S. Pat. No. 6,474,003 to Erickson and Robinson discloses golf shoes having a footbed system with variable sized heel cups.
Another approach is suggested in U.S. Pat. No. 6,598,322 to Jacques. This patent discloses shoes with at least one elongated shape memory alloy element forming laces and an electric circuit. When the circuit is energized, the shape memory alloy shortens and tightens the shoe upper around the foot of a wearer. The circuit is energized by a switch in the heel of the shoe that is turned on by the golfer clicking the heels together. This is not ideal, as it requires the golfer to perform an additional “clicking” action not normally performed when playing golf. An additional abnormal action may interfere with the golfer's performance. This action may also subject the golfer to ridicule. Alternatively, U.S. Pat. No. 6,032,387 to Johnson discloses a shoe with a mechanical tightening and loosening apparatus, which must be manually actuated. Similarly, U.S. Pat. No. 5,839,210 to Bernier et al. discloses a shoe with a shoe tightening apparatus that is also manually actuated.
Performance enhancing footwear is disclosed in U.S. Pat. No. 5,918,502 to Bishop. This patent discloses footwear with a piezoelectric spring apparatus in the sole. Walking or running applies a first force that deforms the spring and generates electrical energy, which is stored in a circuit. When a second force greater than the first force is sensed, such as when a wearer is preparing to jump, the stored energy is released which deforms the spring and imparts a force into the bottom of the sole to assist in the jumping action. This footwear does not address the game of golf and the functional requirements of a golf shoe. Moreover, USGA rules prohibit using shoes with stored energy.
Other sporting devices, such as tennis and racquetball racquets incorporate piezoelectric ceramic fibers to alter their mechanical properties, as disclosed in U.S. Pat Nos. 6,059,674 and 6,106,417. These racquets dampen the vibrations propagating from the hitting surface toward the handle. When the piezoelectric fibers deform, they produce an electrical charge, and vice versa, when a voltage is applied to the piezoelectric fibers, they deform. When a ball impacts the racquet's strings, the impact creates about 50V of voltage from the piezoelectric fibers positioned near the racquet's hitting surface. This discharge is received by an interface circuit in the handle that amplifies the discharge about 7 times and that feeds the discharge back about 5 ms later. This amplified discharge can deflect the racquet up to 1 mm. The vibration caused by the impact is thus reduced up to about 50%. Hence, the vibration created by the impact is received by the circuit, and is amplified and returned with a phase shift to counter the vibrations.
This concept was also applied to skis, where piezoelectric fibers are positioned at about 45° angle to the longitudinal axis of the skis. In one example, an 800V excitation applied to these fibers can twist the skis about 1 cm. These racquets and skis are self-powered and require no battery.
Hence, there remains a need in the art for golf shoes that optimally meet the walking and swinging design requirements without the golfer having to perform any additional actions.